Electrically conductive polydiorganosiloxanes

Abstract

Compositions which cure to electrically conductive silicone elastomers containing greater than 2 percent by weight of phenyl radicals, are disclosed. The compositions comprise a mixture of polydiorganosiloxane and greater than 15 percent by weight of electrically conductive carbonaceous particles of less than 20 micrometers average diameter. Electrically conductive members of controlled resistivity are manufactured using these compositions. These electrically conductive members are useful as the core for improved automotive ignition cable. The ignition cable has a long useful life.

That which is claimed is: 
     
       1. A method of improving the useful electrical life of automotive ignition cable, of the type having a controlled resistivity core, when subjected to high voltage electrical impulses, the method consisting essentially of coating nonmetallic fibers with an electrically conductive composition comprising a polydiorganosiloxane having greater than 2 percent by weight phenyl radicals based on the weight of the composition, the amount of phenyl radical present being increased as the use temperature is increased to that amount necessary to extend the useful electrical life at use temperature, and greater than 15 percent by weight of electrically conductive carbonaceous particles of less than 20 micrometers average diameter, using the coated nonmetallic fibers as the controlled resistivity core. 
     
     
       2. The method of claim 1 in which the nonmetallic fibers are electrically nonconductive. 
     
     
       3. The method of claim 1 in which the nonmetallic fibers are electrically conductive. 
     
     
       4. A method of improving the useful electrical life of automotive ignition cable of the type having a controlled resistivity core when subjected to high voltage impulses, the method consisting essentially of coating nonmetallic fibers with an electrically conductive composition comprising a block copolymer in which there are present polyalphamethylstyrene-styrene blocks and polydimethylsiloxane blocks, the block copolymer having greater than 2 percent by weight phenyl radicals based upon the weight of the composition, the amount of phenyl radical percent being increased as the use temperature is increased to that amount necessary to extend the useful electrical life at use temperature, greater than 15 percent by weight of electrically conductive carbonaceous particles of less than 20 micrometers average diameter, and a hydrocarbon solvent capable of dispersing the composition, using the coated nonmetallic fibers as the controlled resistivity core. 
     
     
       5. The method of claim 4 in which the nonmetallic fibers are electrically nonconductive. 
     
     
       6. The method of claim 4 in which the nonmetallic fibers are electrically conductive. 
     
     
       7. A method of improving the useful electrical life of automotive ignition cable, of the type having a controlled resistivity core, when subjected to high voltage electrical impulses, the method consisting essentially of coating nonmetallic fibers with a composition selected from the group consisting of (a) an electrically conductive composition consisting essentially of a curable vinyldiorganosiloxy endblocked polydiorganosiloxane, the organic radicals being selected from the group consisting of methyl, ethyl, phenyl, and 3,3,3-trifluoropropyl radicals, there being from 0 to 50 inclusive percent 3,3,3-trifluoropropyl radicals and from 0 to 50 inclusive percent phenyl radicals, all percentages of radicals being based on the total number of organic radicals in the polydiorganosiloxane; greater than 15 percent by weight, based on the weight of the composition, of carbonaceous particles of less than 20 micrometers average diameter; a crosslinking agent consisting of a polyorganohydrogensiloxane having an average of at least 2.1 silicon-bonded hydrogen atoms per molecule, said molecules consisting essentially of units selected from the group consisting of H(CH 3 )SiO units, R 2  SiO units, H(CH 3 ) 2  SiO 1/2  units, R 3  SiO 1/2  units, and SiO 2  units, R being selected from the group consisting of alkyl radicals having from 1 to 6 carbon atoms inclusive, phenyl radicals, and 3,3,3-trifluoropropyl radicals, the amount of polyorganohydrogensiloxane being sufficient to provide from 1.2 to 3 inclusive silicon-bonded hydrogen atoms for every silicon-bonded vinyl group in the composition; a platinum-containing catalyst, soluble in the polydiorganosiloxane, and present in an amount sufficient to provide at least 1 part by weight of platinum for every one million parts by weight of the polydiorganosiloxane; an amount of a platinum catalyst inhibitor sufficient to give the desired shelf life; and optionally a phenyl-containing polysiloxane; the composition further restricted in that there must be present greater than 2 percent by weight of phenyl radicals based on the weight of the cured composition, said phenyl radical being present in either the vinyldiorganosiloxy endblocked polydiorganosiloxane, the crosslinking agent, or phenyl-containing polysiloxane separately or in combination and   (b) an electrically conductive composition comprising a block copolymer in which there are present polyalphamethylstyrenestyrene blocks and polydimethylsiloxane blocks, the block copolymer having greater than 2 percent by weight phenyl radicals based upon the weight of the composition; greater than 15 percent by weight of electrically conductive carbonaceous particles of less than 20 micrometers average diameter; and a hydrocarbon solvent capable of dispersing the composition; using the coated nonmetallic fibers as the controlled resistivity core.   
     
     
       8. The method of claim 7 in which the nonmetallic fibers are electrically nonconductive. 
     
     
       9. The method of claim 7 in which the nonmetallic fibers are electrically conductive. 
     
     
       10. An electrically conductive member consisting essentially of electrically conductive nonmetallic fibers bonded together and coated with a cured electrically conductive composition where the composition in the uncured state consists essentially of a curable vinyldiorganosiloxy endblocked polydiorganosiloxane, the organic radicals being selected from the group consisting of methyl, ethyl, phenyl, and 3,3,3-trifluoropropyl radicals, there being from 0 to 50 inclusive percent 3,3,3-trifluoropropyl radicals and from 0 to 50 inclusive percent phenyl radicals, all percentages of radicals being based on the total number of organic radicals in the polydiorganosiloxane; greater than 15 percent by weight, based on the weight of the composition, of carbonaceous particles of less than 20 micrometers average diameter, a crosslinking agent consisting of a polyorganohydrogensiloxane having an average of at least 2.1 silicon-bonded hydrogen atoms per molecule, said molecules consisting essentially of units selected from the group consisting of H(CH 3 )SiO units, R 2  SiO units, H(CH 3 ) 2  SiO 1/2  units, R 3  SiO 1/2  units, and SiO 2  units, R being selected from the group consisting of alkyl radicals having from 1 to 6 carbon atoms inclusive, phenyl radicals, and 3,3,3-trifluoropropyl radicals, the amount of polyorganohydrogensiloxane being sufficient to provide from 1.2 to 3 inclusive silicon-bonded hydrogen atoms for every silicon-bonded vinyl group in the composition; a platinum-containing catalyst, soluble in the polydiorganosiloxane, and present in an amount sufficient to provide at least 1 part by weight of platinum for every one million parts by weight of the polydiorganosiloxane; an amount of a platinum catalyst inhibitor sufficient to give the desired shelf life; and optionally a phenyl-containing polysiloxane; the composition further restricted in that there must be present greater than 2 percent by weight of phenyl radicals based on the weight of the cured composition, said phenyl radical being present in either the vinyldiorganosiloxy endblocked polydiorganosiloxane, the crosslinking agent, or phenyl-containing polysiloxane separately or in combination. 
     
     
       11. The electrically conductive member in accordance with claim 10 in which the vinyldiorganosiloxy endblocked polydiorganosiloxane has a viscosity from 0.1 to 100 Pa.s at 25° C., and the carbonaceous particles consist of carbon or graphite particles present in an amount of between 15 and 40 percent by weight based on the weight of the composition. 
     
     
       12. The electrically conductive member in accordance with claim 10 in which there is present greater than 10 percent by weight phenyl radicals and the carbonaceous particles are present in an amount of between 15 and 40 percent by weight. 
     
     
       13. An electrically conductive member consisting essentially of electrically nonconducting fibers bonded together and coated with a cured electrically conductive composition where the composition in the uncured state consists essentially of a curable vinyldiorganosiloxy endblocked polydiorganosiloxane, the organic radicals being selected from the group consisting of methyl, ethyl, phenyl, and 3,3,3-trifluoropropyl radicals, there being from 0 to 50 inclusive percent 3,3,3-trifluoropropyl radicals and from 0 to 50 inclusive percent phenyl radicals, all percentages of radicals being based on the total number of organic radicals in the polydiorganosiloxane; greater than 15 percent by weight, based on the weight of the composition, of carbonaceous particles of less than 20 micrometers average diameter; a crosslinking agent consisting of a polyorganohydrogensiloxane having an average of at least 2.1 silicon-bonded hydrogen atoms per molecule, said molecules consisting essentially of units selected from the group consisting of H(CH 3 )SiO units, R 2  SiO units, H(CH 3 ) 2  SiO 1/2  units, R 3  SiO 1/2  units, and SiO 2  units, R being selected from the group consisting of alkyl radicals having from 1 to 6 carbon atoms inclusive, phenyl radicals, and 3,3,3-trifluoropropyl radicals, the amount of polyorganohydrogensiloxane being sufficient to provide from 1.2 to 3 inclusive silicon-bonded hydrogen atoms for every silicon-bonded vinyl group in the composition; a platinum-containing catalyst, soluble in the polydiorganosiloxane, and present in an amount sufficient to provide at least 1 part by weight of platinum for every one million parts by weight of the polydiorganosiloxane; an amount of a platinum catalyst inhibitor sufficient to give the desired shelf life; and optionally a phenyl-coating polysiloxane; the composition further restricted in that there must be present greater than 2 percent by weight of phenyl radicals based on the weight of the cured composition, said phenyl radical being present in either the vinyldiorganosiloxy endblocked polydiorganosiloxane, the crosslinking agent, or phenyl-containing polysiloxane separately or in combination. 
     
     
       14. The electrically conductive member in accordance with claim 13 in which the vinyldiorganosiloxy endblocked polydiorganosiloxane has a viscosity from 0.1 to 100 Pa.s at 25° C. and the carbonaceous particles consist of carbon or graphite particles present in an amount of between 15 and 40 percent by weight based on the weight of the composition. 
     
     
       15. The electrically conductive member in accordance with claim 13 in which there is present greater than 10 percent by weight phenyl radicals and the carbonaceous particles are present in an amount of between 15 and 40 percent by weight. 
     
     
       16. An electrically conductive member consisting essentially of nonmetallic fibers bonded together and coated with a cured electrically conductive composition where the composition in the uncured state comprises a polydiorganosiloxane having greater than 2 percent by weight phenyl radicals based on the weight of the composition, the amount of phenyl radical present being increased as the use temperature is increased to that amount necessary to extend the useful electrical life at use temperature, and greater than 15 percent by weight of electrically conductive carbonaceous particles of less than 20 micrometers average diameter. 
     
     
       17. The electrically conductive member of claim 16 in which the nonmetallic fibers are electrically nonconductive. 
     
     
       18. The electrically conductive member of claim 16 in which the nonmetallic fibers are electrically conductive. 
     
     
       19. An electrically conductive member consisting essentially of nonmetallic fibers bonded together and coated with a cured electrically conductive composition where the composition in the uncured state comprises a block copolymer in which there are present polyalphamethylstyrene-styrene blocks, and polydimethylsiloxane blocks, the block copolymer having greater than 2 percent by weight phenyl radicals based upon the weight of the composition, greater than 15 percent by weight of electrically conductive carbonaceous particles of less than 20 micrometers average diameter, and a hydrocarbon solvent capable of dispersing the composition. 
     
     
       20. The electrically conductive member of claim 19 in which the nonmetallic fibers are electrically nonconductive. 
     
     
       21. The electrically conductive member of claim 19 in which the nonmetallic fibers are electrically conductive. 
     
     
       22. An improved automotive ignition cable of the type having a controlled resistivity, electrically conductive member covered with an electrically insulating material wherein the improvement comprises the use of a conductive member consisting essentially of nonmetallic fibers bonded together and coated with a cured electrically conductive composition where the composition in the uncured state comprises a polydiorganosiloxane having greater than 2 percent by weight phenyl radicals based on the weight of the composition, the amount of phenyl radical present being increased as the use temperature is increased to that amount necessary to extend the useful electrical life at use temperature, and greater than 15 percent by weight of electrically conductive carbonaceous particles of less than 20 micrometers average diameter. 
     
     
       23. An improved automotive ignition cable of the type having a controlled resistivity, electrically conductive member covered with an electrically insulating material wherein the improvement comprises the use of a conductive member consisting essentially of nonmetallic fibers bonded together and coated with a cured electrically conductive composition where the composition in the uncured state comprises a block copolymer in which there are present polyalphamethylstyrene-styrene blocks, and polydimethylsiloxane blocks, the block copolymer having greater than 2 percent by weight phenyl radicals based upon the weight of the composition, greater than 15 percent by weight of electrically conductive carbonaceous particles of less than 20 micrometers average diameter, and a hydrocarbon solvent capable of dispersing the composition. 
     
     
       24. An improved automotive ignition cable of the type having a controlled resistivity, electrically conductive member covered with an electrically insulating material wherein the improvement comprises the use of a conductive member consisting essentially of electrically conductive nonmetallic fibers bonded together and coated with a cured electrically conductive composition where the composition in the uncured state consists essentially of a curable vinyldiorganosiloxy endblocked polydiorganosiloxane, the organic radicals being selected from the group consisting of methyl, ethyl, phenyl, and 3,3,3-trifluoropropyl radicals there being from 0 to 50 inclusive percent 3,3,3-trifluoropropyl radicals and from 0 to 50 inclusive percent phenyl radicals, all percentages of radicals being based on the total number of organic radicals in the polydiorganosiloxane; greater than 15 percent by weight, based on the weight of the composition, of carbonaceous particles of less than 20 micrometers average diameter, a crosslinking agent consisting of a polyorganohydrogensiloxane having an average of at least 2.1 silicon-bonded hydrogen atoms per molecule, said molecules consisting essentially of units selected from the group consisting of H(CH 3 )SiO units, R 2  SiO units, H(CH 3 ) 2  SiO 1/2  units, R 3  SiO 1/2  units, and SiO 2  units, R being selected from the group consisting of alkyl radicals having from 1 to 6 carbon atoms inclusive, pheny radicals, and 3,3,3-trifluoropropyl radicals, the amount of polyorganohydrogensiloxane being sufficient to provide from 1.2 to 3 inclusive silicon-bonded hydrogen atoms for every silicon-bonded vinyl group in the composition; a platinum-containing catalyst, soluble in the polydiorganosiloxane, and present in an amount sufficient to provide at least 1 part by weight of platinum for every one million parts by weight of the polydiorganosiloxane; an amount of a platinum catalyst inhibitor sufficient to give the desire shelf life; and optionally a phenyl-containing polysiloxane; the composition further restricted in that there must be present greater than 2 percent by weight of phenyl radicals based on the weight of the cured composition, said phenyl radical being present in either the vinyldiorganosiloxy endblocked polydiorganosiloxane, the crosslinking agent, or phenyl-containing polysiloxane separately or in combination. 
     
     
       25. An improved automotive ignition cable of the type having a controlled resistivity, electrically conductive member covered with an electrically insulating material wherein the improvement comprises the use of a conductive member consisting essentially of electrically non-conducting fibers bonded together and coated with a cured electrically conductive composition where the composition in the uncured state consists essentially of a curable vinyldiorganosiloxy endblocked polydiorganosiloxane, the organic radicals being selected from the group consisting of methyl, ethyl, phenyl, and 3,3,3-trifluoropropyl radicals there being from 0 to 50 inclusive percent 3,3,3-trifluoropropyl radicals and from 0 to 50 inclusive percent phenyl radicals, all percentages of radicals being based on the total number of organic radicals in the polydiorganosiloxane; greater than 15 percent by weight, based on the weight of the composition, of carbonaceous particles of less than 20 micrometers average diameter, a crosslinking agent consisting of a polyorganohydrogensiloxane having an average of at least 2.1 silicon-bonded hydrogen atoms per molecule, said molecules consisting essentially of units selected from the group consisting of H(CH 3 )SiO units, R 2  SiO units, H(CH 3 ) 2  SiO 1/2  units, R 3  SiO 1/2  units, and SiO 2  units, R being selected from the group consisting of alkyl radicals having from 1 to 6 carbon atoms inclusive, phenyl radicals, and 3,3,3-trifluoropropyl radicals, the amount of polyorganohydrogensiloxane being sufficient to provide from 1.2 to 3 inclusive silicon-bonded hydrogen atoms for every silicon-bonded vinyl group in the composition; a platinum-containing catalyst, soluble in the polydiorganosiloxane, and present in an amount sufficient to provide at least 1 part by weight of platinum for every one million parts by weight of the polydiorganosiloxane; an amount of a platinum catalyst inhibitor sufficient to give the desire shelf life; and optionally a phenyl-containing polysiloxane; the composition further restricted in that there must be present greater than 2 percent by weight of phenyl radicals based on the weight of the cured composition, said phenyl radical being present in either the vinyldiorganosiloxy endblocked polydiorganosiloxane, the crosslinking agent, or phenyl-containing polysiloxane separately or in combination. 
     
     
       26. The improved automotive ignition cable of claim 22 wherein the non-metallic fibers are electrically non-conductive. 
     
     
       27. The improved automotive ignition cable of claim 22 wherein the non-metallic fibers are electrically conductive. 
     
     
       28. The improved automotive ignition cable of claim 23 wherein the non-metallic fibers are electrically non-conductive. 
     
     
       29. The improved automotive ignition cable of claim 23 wherein the non-metallic fibers are electrically conductive. 
     
     
       30. The improved automotive ignition cable of claim 24 wherein the vinyldiorganosiloxy endblocked polydiorganosiloxane has a viscosity from 0.1 to 100 Pa.s at 25° C., and the carbonaceous particles consist of carbon or graphite particles present in an amount of between 15 and 40 percent by weight based on the weight of the composition. 
     
     
       31. The improved automotive ignition cable of claim 24 wherein there is present greater than 10 percent by weight phenyl radicals and the carbonaceous particles are present in an amount of between 15 and 40 percent by weight. 
     
     
       32. The improved automotive ignition cable of claim 25 wherein the vinyldiorganosiloxy endblocked polydiorganosiloxane has a viscosity from 0.1 to 100 Pa.s at 25° C., and the carbonaceous particles consist of carbon or graphite particles present in an amount of between 15 and 40 percent by weight based on the weight of the composition. 
     
     
       33. The improved automotive ignition cable of claim 25 wherein there is present greater than 10 percent by weight phenyl radicals and the carbonaceous particles are present in an amount of between 15 and 40 percent by weight.